不同压力条件下氢化丁腈橡胶的应力弛豫及分子动力学模拟研究

采用分子动力学模拟方法构建了氢化丁腈橡胶的分子链结构并计算出不同压缩比下的均方回转半径,同时对应力弛豫进行了理论预测并与压缩应力弛豫实验结果进行了对比.研究发现,均方回转半径随着压力的增大而逐渐降低,随着温度的增大而逐渐增大;在不同压力下,应力均随着时间的增大而逐渐降低而且当时间达到一定程度后应力降低逐渐平缓;计算结果表明压力增大或低温下均方回转半径小、弛豫时间长,体系越表现出弹性特征,此结果表明可用均方回转半径的变化来定量描述橡胶材料体系的应力弛豫变化,分子模拟得到的应力弛豫规律与实验结果有较好吻合.

STUDY ON THE STRESS RELAXATION OF HNBR BY MOLECULAR DYNAMICS SIMULATION AT DIFFERENT PRESSURES

The stress relaxations of HNBR were studied by molecular dynamics(MD) simulation.The structure of hydrogenated nitrile butadiene rubber(HNBR) was constructed and several circles of energy minimization(MM) and MD simulation were applied.The distribution function of gyration radius was calculated under different compression ratios and temperatures.The fitting functions of normal stress with time under different pressures were obtained.Compression stress relaxation experiment of different compression ratios was also conducted.Comparing with the coefficient of stress relaxation from the experiment,it was found that the theoretical stress relaxation curves were similar to the experimental data.The results indicated that the mean-square radius of gyration decreased with the enhancement of pressure and it decreased with the reduction of temperature,which corresponded to the typical viscoelasticity stress relaxation behaviors of polymers.It is confirmed that the variation of mean-square radius can be used to quantitatively describe the stress relaxation of rubber system and a good agreement between the theoretical curves with the experimental data can be obtained from MD simulation.